The term Jacob's staff, also cross-staff, a ballastella, a fore-staff, or a balestilha, is used to refer to several things. This can lead to considerable confusion unless one clarifies the purpose for the object so named. The two most frequent uses are:
- in astronomy and navigation for a simple device to measure angles, later replaced by the more precise sextants;
- in surveying for a vertical rod that penetrates the ground and supports a compass or other instrument.
Read more about Jacob's Staff: Astronomy and Navigation, Surveying
Famous quotes containing the words jacob and/or staff:
“As for me, Abraham, Isaac, and Jacob are now only the subtlest imaginable essences, which would not stain the morning sky.”
—Henry David Thoreau (1817–1862)
“Man, in spite of his tendency towards mendacity, has a great respect for what he calls the truth. Truth is his staff in his voyage through life; commonplaces are the bread in his bag and the wine in his jug.”
—Rémy De Gourmont (1858–1915)